Heating element and method of production



Oct. 30, 1945. A. .1. HUCK f 2,387,995

HEATING ELEMENT AND METHOD OF PRODUCTON Filed March l, 1944 INVENTOR./l/f A067( Patented Oct. 30, 1945 HEATING ELEMENT AND METHOD OFPRODUCTION Alfred J. Huck, St. Louis, Mo., assignor to Knapp- MonarchCompany, St. Louis, Mo., a corporation of Missouri Application March 1,1944, Serial No. 524,550

7 Claims. (Cl. 201-67) My present invention relates to a heating elementwhich can be formed in a relatively flattened shape and therebyparticularly adapted for heating pads or the like, and to a method ofproducing such heating element.

One object of the invention is to provide a heating element of simple,durable and inexpensive construction which is flattened in cross sectionas distinguished. from the usual round heating element, my elementaccordingly reducing the over-all thickness of a heating pad or the likeand minimizing the ridges on the padnormally present where round heatingelements are used.

Another object is to provide a heating element which is elliptical incross section and a method of making it which comprises the steps offorming the heating element of such materials that it can be flattenedwithout danger of short-circuiting the turns of the resistance coil andthe flattening of the element gives it the desired elliptical shape andminimizes its final thickness.

With these and other objects in View, my invention consists in theconstruction, arrangement and combination of the various parts of theheating element and in the steps of the method for forming it wherebythe objects contemplated are obtained as hereinafter more fully setforth, pointed out in my claims and illustrated in the accompanyingdrawing wherein:

Figure 1 is a plan View of my heating element sewed to a backing sheetfor the purpose of forming the inner portion of a heating pad or thelike.

Figure 2 is an enlarged elevation of the heating element showing partsof the ends broken off to illustrate the various components of theelement.

Figure 3 is an enlarged cross sectional View of the heating elementafter it is assembled.

Figure 4 is a side elevation o-f the heating element showing it beingattened between a pair of rollers.

Figure 5 is a sectional view similar to Figure 3 showing the crosssection after ilattening; and

Figure 6 is a longitudinal sectional view through the heating element onthe line 6 6 of Figure 5, part of the ligure being unsectioned to moreclearly show the construction.

On the accompanying drawing I have used the reference character H toindicate in general a heating element. A core therefor is shown at I andmay be formed of asbestos bers or other suitable insulating andheat-resisting material which is flexible and of a deformable nature.Wound around the core I0 is a resistance wire I2 of suitable size forthe wattage with which it is to be energized. lIhe resistance wire I2 iswound tightly on the core Ill so as to press into its surface as shownin Figure 6.

After the resistance wire is wound on the core, a plurality of asbestosthreads Ill are wound on the core and resistance coil to form a covertherearound. The threads I4 likewise are flexible and deformable.Finally a plurality of linen or cotton threads I6 are wound on the coverI4 and in the opposite direction to its winding for the purpose ofretaining the elements I0, I2 and I4 assembled so that a completeheating element is thereby provided, which can be handled for subsequentsteps of the method herein disclosed` without electrically exposing anyportion of the resistance coil.

In Figure 3 I illustrate the cross section of the heating element afterit is formed in accordance with the foregoing method and the neXt stepin the method is to flatten the heating element to the shape shown inFigure 5. This may be done between the dies of a press or by merelypassing the heating element between a pair of rollers I8 and 20 (seeFig. 4).

The rollers are suitably driven and are properly spaced to secure thedesired degree of flattening. The heating element is fed to the rollers,as at the left side of Figure 4, and comes out at the right sideflattened as illustrated at Figure 5.

The flattening process does not in any way harm the heating element asthe members I0, I4 and I6 thereof are all readily deformable and thewire I2, of course, can be readily bent from circular shape toelliptical shape. The wire tends to stay in this shape and adjacentcoils of the wire, I iind, are not short-circuited with relation to eachother but remain substantially equally spaced as originally wound Theresultant structure, however, is a well attened heating element as shownin Figure 5 having about half the thickness of the one shown in Figure3. Subsequently the heating element may be sewed to a backing sheet 22,bythe usual heating element sewing machine which sews across the elementwith threads indicated at 23, the backing sheet 22 preferably being awoven asbestos cloth.

Figure 6 illustrates how the cover I4 is tightly wound on the coil I2and nally the threadsJb` tightly wound around the cover so as to biteinto the cover and effectively hold the parts of the heating elementassembled. The resulting structure, after flattening, makes it possibleto form a heating pad or the like of considerably less thickness than atpresent and one in which the ridges formed by the heating element aremuch less conspicuous to the touch and more comfortable against the bodywhen the heating pad is in use.

Some changes may be made in the construction and arrangement of theparts of my heating element and the method of producing it may be variedto some extent without departing from the real spirit and purpose of myinvention. Accordingly it is my intention to cover by my claims anymodified forms of structure'or use of mechanical equivalents orequivalent methods which may be reasonably included Within their scopeWithout however sacrificing any of the advantages of the invention.

I caim as my invention and desire to secure by United States LettersPatent:

1. A heating element for a heating pad or the like comprising a flexiblecore of asbestos, elliptical in cross section, a coil of resistance wireWound tightly therearound, said coil being elliptical in cross sectionand helically elliptical in form, a cover of flexible asbestos Woundaround said coiled Wire and core and a Winding of thread around saidcover in the opposite direction to retain said core, coil and coverassembled.

2. A heating element for heating pads or the like comprising aexiblecore of insulation, a coil of resistance Wire wound therearound, acover of exible insulation wound around said coiled Wire and core, and aWinding of thread around said cover to retain said core, coil and coverassembled, said core, coil and cover being elliptical in cross sectionand said coil being helically elliptical.

3. In a heating element of the kind disclosed, a flexible core, ahelical coil of resistance Wire Wound thereon, a exible cover aroundsaid coiled Wire and core, said core, coil and cover being e1- lipticalin cross section.

4. In a heating element of the kind disclosed, a exible core, a coil ofresistance Wire wound thereon, a flexible cover around said coiled Wireand core, said core, coil and cover being flattened in cross sectionwith said coil and retaining its helical form secured flatwise toabacking sheet.

5. A method of producing a heating element comprising the steps ofWinding a resistance wire helically around a flexible deformable core,winding a exible deformable cover around said resistance Wire, Windingthreads around said cover to retain the foregoing elements assembled,at-

tening the assembly between rollers to decrease the thickness of theassembly and retain said resistance wire in helical form, and sewing theflattened heating element assembly on a supporting sheet for use in aheating pad or the like.

6. A method of producing a heating element for a heating pad or the likecomprising the steps of helically winding a resistance Wire around aflexible vdeformable core, Winding a flexible de- ALFRED J. HUCK.

